1. Field of the Invention
This invention relates to linear controlled resistance means for controlling the amount of resistance in an electric circuit.
2. Description of the Prior Art
Variable resistors are used in the electrical field for various applications such as controlling the volume of audio equipment. It is well known by persons skilled in the variable resistor art that lineal controlled variable resistors offer the advantages of ease of manipulation and of quick identification of the amount of resistance of the resistor while rotary controlled variable resistors offer the advantage of ease of fine adjustment. As evidenced by Chantemerle, U.S. Pat. No. 1,351,023; Miyashita, U.S. Pat. No. 3,743,999; and Murao et al., U.S. Pat. No. 3,800,266, variable resistor units which combine the advantages of both lineal and rotary controlled variable resistors have been developed. None of these patents disclose or suggest the present invention.
The known variable resistor units which combine the advantages of both lineal and rotary controlled variable resistors have not proved entirely satisfactory because of various reasons. In Chantemerle, a plunger coacts with the shaft of a rotary controlled variable resistor so that when the plunger is moved in and out, the resistance of the rotary controlled variable resistor will be varied. This device is not entirely satisfactory since identification of the amount of resistance being applied depends upon how far the plunger extends past the shaft which does not lend itself to quick determination. In Miyashita, a lever is pivotally mounted to the frame of a variable resistor unit. One end of the lever coacts with the shaft of a rotary controlled variable resistor so that when the lever is moved up and down, the resistance of the rotary controlled variable resistor will be varied. This device is not entirely satisfactory since the maximum amount the resistance can be varied depends upon the maximum amount the lever is capable of pivoting which is limited. In Murao et al, a rotary controlled variable resistor is slidably mounted to the frame of a variable resistor unit. A pulley is attached to the shaft of the rotary controlled variable resistor. A string is affixed to the pulley and to the frame in such a way that back and forth movement of the variable resistor within the frame will cause the resistance of the rotary controlled variable resistor to be varied. This device is not entirely satisfactory since the string-and-pulley arrangement of control is somewhat unreliable.